Planer device for the automatic extraction of coal and the like



Jan. 15, 1963 LOBBE 3,073,581 PLANER DEVICE FOR THE AUTOMATIC- EXTRACTION OF COAL AND THE LIKE Filed April 12, 1960 2 Sheets-Sheet l l3 ISL INVENTOR MMm/ 4 5886' B Jan. 15, 1963 A. LGBBE y 3,073,581

PLANER DEVICE FOR THE AUTOMATIC EXTRACTIQN OF COAL AND THE LIKE Filed April 12, 1960 2 Sheets-Sheet 2 INVENTOR AIM/A A5835 United States Patent Ofiiice 3,073,581 Patented Jan. 15, 1963 The present invention relates to a planer device adapted to be passed along a longitudinal path in contact With a face of mineral material, such as coal, in order to extract the same. More particularly, the invention relates to a planer assembly for the extraction of lateral walls of coal as well as overhead coal disposed along the roof of the mine stay.

Generally speaking, in accordance with customary procedures long-wall mine extraction is carried out by scaling of]? or chipping off the mineral along the mine face by passing the planer device back and forth therealong. As a consequence, the overhead coal disposed along the roof of the mine stay becomes loose, since it is robbed of its support, and automatically falls and is recovered. Depending upon the quality of the coal or other mineral being extracted, as well as upon the type of formation of the overlying strata, however, the overlying coal in the roof portion frequently does not automatically collapse and fall but remains instead only partially loosened. It is then necessary to assist the removal of this overhead coal manually, such as by means of pick axes, air hammers and other similar devices.

It is an object of the present invention to overcome the foregoing disadvantages and to provide a planer assembly of the foregoing type which is adapted to be passed along a longitudinal path in contact with the coal to be removed so as to remove the overlying coal in the roof of the mine stay as well as the lateral walls of coal normally removed by planer devices.

It is another object of the present invention to provide a planer assembly which includes oppositely disposed, spaced apart, inter-connected base members having guide means pivotally connected at one end to the base members and pivotally connected to one another at their other ends so as to form an adjustable angle guide support structure. In this way, cutting means disposed at the inter-connection between said other ends of the guide means may be raised and lowered into and out of cutting engagement with the overlying coal in the roof of the mine stay being worked.

These and further objects of the invention will become apparent from a study of the within specification and accompanying drawing in which:

FIGURE 1 shows the arrangement of a planer assembly in accordance with the invention with respect to a mine stay being worked in side elevation;

FIGURE 2 is an end view of a planer assembly corresponding to that of FIGURE 1 illustrating the manner in which the overlying coal may be extracted;

FIGURE 3 and FIGURE 4 correspond to the embodiment of a planer assembly illustrated in FIGURES l and 2 wherein, however, the cutting means is raised to the maximum height of use;

FIGURE 5 is a side elevation view of an embodiment of the invention illustating the manner in which the same is operated with respect to an overlying coal seam of uneven thickness;

FIGURE 6 illustrates in enlarged schematic section the manner in which the cutting means are attached to the drive means of the planer assembly; and

FIGURE 7 illustrates in enlarged schematic side view the arrangement of FIGURE 6 illustrating the structural 2 relation between the cutting means and the guide means elements upon which the same are mounted.

In accordance with the present invention, it has been found that a planer assembly may be provided which assures a mechanical extraction of coal throughout the entire long wall of the mine stay from the top to the bottom of the scam in lateral increments. The planer assembly of the invention is advantageously constructed as a double-planer, i.e. one having a pair of oppositely disposed, spaced apart base members inter-connected by Y a resilient connecting means and adapted to be passed along a longitudinal path of travel in contact with the mine face to be extracted. By means of a conventional endless chain driving arrangement, the base members may be passed back and forth along the longitudinal path in contact with the mine face so as to cuttingly engage and loosen the coal by means of cutting tools mounted on the base members for this purpose. Upon cutting into the mine wall a lateral distance approximately equal to the width of the planer assembly, for example, additional cutting tools also equal to this width which are mounted on the guide means may be brought into play to extract the coal in the overlying roof portion.

Specifically, a pair of oppositely disposed guide means, each pivotally connected at one end to a corresponding base member and pivotally connected to one another at their other ends by a hinge means are employed for sup porting the cutting means for extractingthe overlying roof coal. By adjusting the linear distance between the pivotal connections of the guide means to the base members, the angle formed by the guide members is changed and in turn the cutting means are raised or lowered into and out of contact with the overlying roof coal to be extracted.

Thus, after the cutting tools on the base members have extracted the coal in lateral direction, the roof cutting means mounted on the guide means may be brought into play to extract in an upward direction the overlying roofcoal. For this purpose means are provided for shortening the linear distance between the pivotal connections of the guide means to the base members so as to raise the roof cutting means in increments. In this way during the back and forth path of travel of the roof cutting means, the same may cut into and disengage successive layers of coal in the overlying roof formation.

At least one and preferably both of the oppositely disposed base members is provided with cutting tools for extracting coal in lateral direction, a vertical distance corresponding to the height of said cutting tools. As the planer is inwardly worked into the lateral mine wall, coal is extracted only to the height of the cutting tools which generally corresponds to the height of the base members.

I This height necessarily only amounts to a fraction ofthe entire height of the seam of coal to be extracted. When the base members have removed sufiicient lateral coal so that the width of the overlying seam thereabove approximately corresponds to the width of the roof cutting tools, the roof cutting tools may be upwardly raised and urged into back and forth cutting engagement with the overlying coal. Upon reaching the top of the seam, the roof cutting tools may be lowered once again and the operation repeated, starting with the lateral extraction of coal by means of the base member cutting tools.

Advantageously the guide means are constructed in the shape of frames having a width at least corresponding to the base member width and preferably slightly wider than the same. The guide means are preferably interconnected at their outer ends by means of a common shaft directed approximately transversely with respect to the longitudinal direction of travel of the planer assembly. The roof cutting tools, of course, are suitably mounted on the shaft so that the same may be raised and lowered into cutting engagement with the overlying roof coal. It is also advantageous if the cutting tools attached to the shaft are rockingly mounted so that the same may be tilted back and forth within a limited angle with respect to the vertical. The particular structuralarrangement for limiting the tilting movement to one side or the other of the cutting means may be varied. Thus, for example, a support bar may be positioned on each of the frame-shaped guide means or guide bars, parallel to the shaft interconnecting the same. On these support bars may be disposed one or more symmetrically formed supporting link elements of U-shaped configuration. These link elements may engage along their U-shaped surfaces corresponding fiattenings in the inter-connecting shaft of the frame-shaped guide means or guide bars. In this way a very specific vertical adjustment of the link elements may be carried out with respect to the cutting tools and interconnecting shaft independently of the particular height of the frame-shaped guide means. The link elements are provided therebetween with oppositely disposed bearing means which loosely engage a downward continuation of the cutting tools. A desired limited clearance between the continuation of the cutting tools and the bearing means is provided so that a slight rocking to and fro of the cutting tools may be effected. Since the roof cutting tools are advantageously provided as bilateral cutting tools by executing the rocking movement of the cut-ting tools one or the other of the bilateral cutting portions will come into play with the overlying coal.

The oppositely disposed base members of the planer assembly are advantageously coupled to one another in the longitudinal direction of movement of the assembly by means of a resilient inter-connecting element, such as a tension spring. Therefore, if the roof cutting tools, positioned at the vertex of the guide means, encounter an increase in resistance, the stresses thereon are advantageously passed along the guide means to the base members whereby under such additional resistance, the tension spring is caused to stretch. In this manner the angle defined between the inter-connected guide means is increased and the roof cutting tools are lowered out of engagement with the mine roof thereat. It will be appreciated that the height of the roof cutting tools is directly dependent upon the linear distance apart of the pivotal connections between the guide means and the base members. By increasing or decreasing this linear distance, the angle between the guide means is changed as well as the height of the roof cutting tools. Nevertheless, if the distance between the oppositely disposed base members is changed, as by increasing the tension on the inter-connecting spring, this factor will influence the particular height of the roof cutting tools.

Thus, each of the base members is provided with a transveerse bore hole, for example, for pivotally connecting the same to a corresponding frame-shaped guide means. Inasmuch as the linear distance between said pivotal connections must be varied in order to raise and lower the roof cutting tools, at least one of the base members must be provided with a series of such bore holes, one after the other, so that the pivot point with the frame-shaped guide means may be selected along a predetermined longitudinal extent of the corresponding base member. Alternatively, for example, other means may be provided for the adjustable distance pivotal connection of at least one of the guide means to a base member, such as a sliding track connection disposed along the particular base member.

In order to lift the roof cutting tools, one or both of the frame-shaped guide means may be provided with a suitable lifting device for varying the slanting position of the guide means with respect to the horizontal. Such a device may be either automatically or manually operable, such as a piston cylinder arrangement activated by hydraulic means for raising and lowering a corresponding frame-shaped guide means. The provision for this hydraulic piston cylinder arrangement advantageously allows for the dampening of the spring action of the tension spring to thereby effect a uniform contact pressure between the roof cutting means and the overlying coal.

Optionally, at the vertex of the two oppositely disposed guide means a skid projection should be provided which extends vertically beyond the upper end of the cutting means so as to prevent a further cutting of the overlying coal when the desired height of cutting has been reached (see FIGURE 4).

Specifically, in the overall operation, the oppositely disposed frame-shaped guide means are lowered to their lowermost position along with the roof cutting tools. Then, in the customary manner the extraction of the coal in lateral direction is carried out using the cutting means disposed on the planer assembly. With each back and forth movement of the base members, there is extracted a rough cut of specific height. Before each subsequent passage of the planer assembly is carried out, however, the guiding track on which the assembly is drawn back and forth, is advanced toward the coal seam being cut a distance equal to the amount of coal extracted during the last passage. This operation is repeated until the desired lateral depth of the under-coal extraction has been reached. This generally is equal to the width of the roof cutting means of the planer assembly. When this point has been reached, the guiding track is secured in position and the frame-shaped guide means carrying the roof cutting means are raised a slight degree. In the next passage of the planer assembly, the roof cutting tools extract the coal lying in the roof with immediately above the assembly. Since the assembly is not advanced inwardly for further cutting of the lateral seam, the cutting. means on the base members do no engage the coal. At the end of a run, the guide means are raised further by means of the lifting device so as to cuttingly engage the coal lying immediately thereabove.

If at any place along the roof, the resistance met by the roof cutting tools attached to the guide means is too great, then the guide means pass this resistance to the interconnecting tension spring between the base members whereby the linear distance between the pivotal connections of the lower ends of the guide means to the base members is changed. Under certain circumstances, in this regard, it may be necessary to draw the planer assembly several times along the overlying mine face before again raising the position of the roof cutting means. When the upward cutting of the seam has been completed, the upwardly extending skid prevents further extraction of coal in upward direction.

Referring to the drawings a planer assembly is shown including a pair of base members 10 and 11, which are coupled together by means of an elongated tension spring 12. At the remote ends of the base members 10 and 11 an endless drive chain 13 is attached for passing the planer assembly along a longitudinal path of travel in contact with the mine face to be worked in the customary manner. The planer assembly is mounted for travel along a guide rail or pipe 14 which is positioned along the coal face to be worked adjacent a conventional conveyor for coal which has been extracted. The oppositely disposed base members 10 and 11 are additionally connected together by means of a pair of oppositly disposed guide frames 16 and 17 which are in turn connected at their outer ends with one another by means of a shaft 18. Guide frame 16 is connected to base member 10 by means of a cross bolt 19 while guide frame 17 is connected to base member 11 via cross bolt 20. As may be seen in FIGURE 3, base member 11 is provided with a series of parallel transverse bore holes 21, each of which may serve for the pivotal support and connection for bolt 20. As the linear distance between the pivotal connection of cross bolt 19 to base member 10 and the connection of bolt 20 to base member 11 decreases, the guide frames 16 and 17 are raised, in turn raising the vertical position of shaft 18.

According to FIGURE 1 bolt 24) is placed in the outermost bore hold of base member 11 increasing to a maximum the linear distance between the pivotal connections of the guide frames 16 and 17 to the corresponding base members and 11. At this point the cutting tools 22 are in lowermost position, out of cutting engagement with the coal seam. As may be seen from FIG- URE 2 at this point a lateral cutting of the mine face takes place by means of the cutting tools arranged on base members 10 and 11 adjacent the mine face being worked. On the other hand, FIGURE 3 illustrates the smallest linear distance between the pivotal connections of guide frames '16 and 17 to base members 10 and 11 respectively. In this instance, the shaft is at the uppermost vertical position and the cutting tools 22 are in uppermost engagement with the overlying roof coal 38. FIGURE 4, in comparison to FIGURE 2, indicates that a lateral layer of coal, corresponding approximately to the width of the guide frames 16 and 17 has been completely extracted, the skid 42 extending to the side of cutting tools 22, remote from the lateral mine face 36 preventing further extraction of coal in upward direction. This may be seen more clearly from a study of FIGURE 2 wherein the under-coal face 37 to be extracted in upward direction does not extend outwardly over skid 42. However, when skid 42 engages the over head face 38, as shown in FIGURE 4, the cutting tools are prevented from further extracting coal.

In each of FIGURES 2 and 4 a conveyor assembly is illustrated, which may be of conventional design, such as a double chain scraper conveyor. It will be appreciated that as the coal is loosened from the mine face, the same is outwardly urged so that it falls on to the conveyor 15 for ultimate removal from the extraction site.

As may be seen from FIGURE 6, each of the cutting tools 22 is bilaterally executed, having cutting edges 23 and 24 for cutting in either direction of movement. The cutting tools 22 are tiltable around the angle alpha so that during each forward movement of the planer assembly cutting edge 24 comes into play with the overlying coal while in each return movement cutting edge 23 comes into play. By rockingly positioning cutting tools 22 on shaft 18, only one cutting edge of the cutting tools is in use at a time with the result that any unnecessary friction'on the moving parts is avoided. The tilting disposition of cutting tools 22 on the shaft 18 is determined by means of the lower continuation 25 of cutting tool 22 moving between bearing surfaces 26 of limiting connections 28 and 29 bilaterally disposed be tween spaced apart link or link elements 27. The bilateral distance between the bearing surfaces 26 of connections 28 and 29 is greater than the width of continuation 25 of tool 22 by an increment corresponding to the angle alpha. The link elements 27 are loosely positioned by means of supporting surfaces 30 and, 31 respectively onto symmetrically positioned supporting bars 32 and 33 which run parallel to shaft 18. Supporting bar 32 is connected to guide frame 16 while supporting bar 33 is connected to guide frame 17. Link element 27 is further provided with a U-shaped intermediate portion 34 guidingly engaging in tight contact with corresponding flattenings 35 of shaft 18. Each of the links or link elements 27 interconnected by limiting connecting means 28 and 29 may move in a vertical direction according to the length of the U-shaped portion in dependence upon the pivotal movement of guide frames 16 and 17. Due to the coop crating engagement between the U-shaped portion 34 and the flattenings 35, the link elements maintain their horizontal relation during vertical upward and downward movement of the vertex connection of frames 16 and 17 at shaft 18. I

In this same connection, the guide surface 26 is simultaneously always maintained in precisely perpendicular position with respect to the path of travel of the planer assembly. Accordingly, the tools 22 are always upwardly directed in any position of the guide frames 16 and 17 and the limited tiltability of the tools 22 within the angle alphais preserved.

In order to make possible the upward extraction of the overlying coal 36, the pivotal connection of bolt 20 on base member 11 must be reset successively into the various transverse bore holes 21. Starting with the outermost bore hole21, the pivotal positioning of guide frame 17 is changed until the same is effected by passage of bolt 20 to the innermost bore hole 21. A hydraulic pump 39, actuated by means of a manual lever 40, is used to fill a pressure cylinder 41 to a predetermined extent in order to raise the guide frames 16 and 17 correspondingly. In this 'way the cutting tools 22 are upwardly urged in increments so that successive layers of overlying coal may be extracted during back and forth passage of the planer assembly along the longitudinal path of travel. It will be understood that the raising and the lowering by means of pressure cylinder 41 and pump 39 of the guide frames 16 and 17 must be carried out in conjunction with the changing of the pivotal connection between guide frames 17 and base member 11 via bolt 20 and bore holes 21 along the linear extent 21a. When guide frames 16 and 17 are in their lowermost positions, with bolt 20 being received within the outermost bore 21, spring 12 will be placed under slight tension. As the guide frames 16 and 17 are raised and the linear distance between bolt 19 and bolt 20 decreases the tension on spring 12 will be relieved.

If the overlying seam of coal is uneven along any portion, as illustrated in FIGURE 5 of the drawings, then by means of skid 42, the cutting tools 22 are downwardly urged out of contact with such overlying seam. Due to the presence of the hydraulic pressure means, including cylinder 41, and pump 39 a dampening of the forces exert ed by reason of the unevenness of the mine roof 38 will be effected. The angle defined between the guide frames 16 and 17 in turn will increase whereby the spring 12 will be stretched a corresponding amount. Cylinder 41 is suitably provided with means for allowing at least a part of the hydraulic pressure fluid to flow back into the reservoir therefor during this dampening action. When the height of the overlying seam of coal again increases, then the spring 12 contracts to its former length and the cutting tools 22 are again raised to the desired level. The overhead extraction of coal may therefore be continued as before. It will be seen that in this way no damage to the planer assembly will take place by reason of the unevenness of the overlying mine face 38 due to the provision for dampening the excessive forces by means of cylinder 41 and the absorption of the stresses exerted via cutting tools '22 and guide frames 16 and 17 by means of tension spring 12.

As an optional feature of the invention, the side of guide frames 16 and 17 adjacent the lateral coal face 36 to be extracted, in each instance is suitably provided with cutting edges (see edge 43 in FIG. 4) so as to avoid binding between the guide frames and the lateral mine face and to eifect eificiently the further extraction of coal.

All in all a suitable planer assembly is provided in accordance with the invention which permits the efiicient extraction of coal in upward direction in addition to the extraction of coal in lateral direction using an upwardly adjustable cutting means provided on a hinge means connection between supporting guide frames of the planer assembly. The provision for changing the angle between the supporting guide means and absorbing excessive forces by means of a tension spring afford excellent practical applications for the construction of the present invention.

What is claimed is:

1. A planer assembly adapted to be passed along a longitudinal path in contact with a face of mineral material to be extracted which comprises oppositely disposed spaced apart base members interconnected by and normally biased toward each other by resilient connecting means, oppositely disposed guide means each pivotally connected at one end to a corresponding base member and pivotally connected to one another at their other ends by a hinge means, the linear distance between the pivotal connections of said guide means to said base members being adjustable longitudinally, and cutting means disposed on said hinge means for cuttingly engaging an adjacent face of mineral material to be extracted.

2. A planer according to claim 1 wherein said resilient connecting means changes in length in dependence upon changes in longitudinal tension exerted thereon by changes in the distance between said spaced apart base members.

3. A planer according to claim 1 wherein at least one of said base members and said guide means is provided with additional cutting means adapted to engage a laterally adjacent face of mineral to be extracted upon passage of the planer assembly along said longitudinal path.

4. A planer according to claim 1 wherein said base members are mounted for movement along said longitudinal path and are urged along by a pulling means attached thereto.

5. A planer according to claim 1 wherein said cutting means are rockingly disposed on said hinge means, said hinge means being provided with oppositely disposed bearing means for limiting the rocking angle of said cutting means with respect to a plane substantially normal to the longitudinal path of travel.

6. A planer according to claim 1 wherein said base members are slidably mounted on a guide rail element for movement therealong.

7. A planer according to claim 1 wherein adjustable longitudinal positioning means are provided for pivotally connecting the guide means of a corresponding base member to the base member along a variable longitudinal extent thereof whereby the linear distance between the pivotal connection of said guide means to said corresponding base member and the pivotal connection of the other guide means to the other base member may be adjusted longitudinally.

8. A planer according to claim 7 wherein said base member is provided with a plurality of base member pivot seating means arranged along a longitudinal extent thereof and said guide means is provided with a cooperating guide means pivot seating means adapted to engage said base member pivot seating means to adjust the connection therebetween along said variable longitudinal extent.

9. A planer according to claim 7 wherein upon adjusting the longitudinal positioning of the pivotal connection of said guide means to the base member in one linear direction, the outer ends of the oppositely disposed guide means and the hinge means are simultaneously laterally outwardly directed with respect to the longitudinal path, and upon adjusting the longitudinal positioning of said pivotal connection in the other linear direction, the outer ends of the oppositely disposed guide means and the hinge means are simultaneously laterally inwardly directed with respect to the longitudinal path.

10. A planer according to claim 7 wherein a hydraulic piston-cylinder arrangement is provided on said planer assembly for inwardly and outwardly directing the outer ends of the oppositely disposed guide means in conjunction with the adjusting of the longitudinal positioning of the pivotal connection of said guide means to the corresponding base member.

11. A planer assembly adapted to be passed back and forth along a longitudinal path of travel in contact with a face of mineral material to be extracted which comprises a pair of oppositely disposed spaced apart base members interconnected by and normally biased toward each other by a resilient connecting means, a pair of oppositely disposed guide means, each pivotally connected at one end to a corresponding base member and hingedly connected to one another at their other ends by a common hinge means having a common axis of rotation disposed generally transverse to the longitudinal path of travel and parallel to the pivotal axes of connection of the guide means to the corresponding base members whereby to form a triangular linkage having a common apex defined by said common axis and a base defined by the distance between the pivotal connections of said guide means to the corresponding base members, and cutting means limitedly rockingly disposed along said hinge means with respect to said axis of rotation and having bilateral cutting edges for alternately cuttingly engaging an adjacent face of mineral material to be extracted situated along the back and forth path of travel of said cutting means, the pivotal connection of one of said guide means to the corresponding base member being positioningly adjustable along a longitudinal extent of said base member whereby to outwardly and inwardly pivot said guide means and in turn move said cutting means transversally outwardly and inwardly with respect to said longitudinal path of travel.

12. A planer assembly according to claim 11 wherein hydraulic means are provided for outwardly and inwardly pivoting said guide means and in turn moving said cutting means with respect to said longitudinal path of travel in conjunction with the adjusting of the longitudinal positioning of the pivotal connection of said guide means to the corresponding base member.

13. A planer assembly adapted to be passed along a longitudinal path in contact with a face of mineral material to be extracted which comprises oppositely disposed spaced apart base members interconnected by resilient connecting means, oppositely disposed guide means each pivotally connected at one end to a corresponding base member and pivotally connected to one another at their other ends by a hinge means, the linear distance between the pivotal connections of said guide means to said base members being adjustable longitudinally, and cutting means disposed on said hinge means for cuttingly engaging an adjacent face of mineral material to be extracted, a skid means being provided on said hinge means extending upwardly slightly beyond the cutting means and positioned at one side of the cutting means to prevent engagement of said cutting means with the face of the mineral material Where said skid means is in abutment with said face.

14. A planer assembly adapted to be passed back and forth along a longitudinal path of travel in contact with a face of mineral material to be extracted which comprises a pair of oppositely disposed spaced apart base members interconnected by a resilient connecting means, a pair of oppositely disposed guide means, each pivotally connected at one end to a corresponding base member and hingedly connected to one another at their other ends by a common hinge means having an axis of rotation disposed generally transverse to the longitudinal path of travel and parallel to the pivotal axes of connection of the guide means to the corresponding base members, and cutting means limitedly rockingly disposed along said hinge means with respect to said axis of rotation and having bilateral cutting edges for alternately cuttingly engaging an adjacent face of mineral material to be extracted situated along the back and forth path of travel of said cutting means, the pivotal connection of one of said guide means to the corresponding base member being positioningly adjustable along a longitudinal extent of said base member whereby to simultaneously outwardly and inwardly pivot said guide means and in turn move said cutting means transversally outwardly and inwardly with respect to said longitudinal path of travel, skid means being provided on said hinge means extending upwardly slightly beyond the cutting means and positioned at one side of the cutting means to prevent engagement of sa d cutting means with an adjacent face of mineral material where said skid means is in abutment with said face.

15. A planer assembly adapted to be passed back and forth along a longitudinal path of travel in contact with a face of mineral material to be extracted which comprises a pair of oppositely disposed spaced apart base members interconnected by a resilient connecting means, a pair of oppositely disposed guide means, each pivotally connected at one end to a corresponding base member and hingedly connected to one another at their other ends by a common hinge means having an axis of rotation disposed generally transverse to the longitudinal path of travel and parallel to the pivotal axes of connection of the guide means to the corresponding base members, and cutting means limitedly rockingly disposed along said hinge means with respect to said axis of rotation and having bilateral cutting edges for alternately cuttingly engaging an adjacent face of mineral material to be extracted situated along the back and forth path of travel of said cutting means, the pivotal connection of one of said guide means to the corresponding base member being positioningly adjustable along a longitudinal extent of said base member whereby to simultaneously outwardly and inwardly pivot said guide means and in turn move said cutting means transversally outwardly and inwardly with respect to said longitudinal path of travel, said hinge means including a shaft, said shaft having flattened side portions, a U-shaped member guidingly disposed on said shaft at said flattened side portions, each of said guide means additionally carrying a support bar parallel to said shaft, said U-shaped member having bilateral loop means and being mounted on each said support bar via said bilateral loop means for maintaining horizontal disposition of said U-shaped member during inward and outward movement of said guide means, said U-shaped means having bilateral bearing means for limiting the angle of rocking of said cutting means by engagement therewith.

References Cited in the file of this patent UNITED STATES PATENTS 2,566,003 Vogel Aug. 28, 1951 2,670,943 Vogel Mar. 7, 1954 20 2,745,651 Herrmann May 15, 1956 FOREIGN PATENTS 914,724 Germany July 8, 1954 769,328 Great Britain Mar. 6, 1957 

1. A PLANAR ASSEMBLY ADAPTED TO BE PASSED ALONG A LONGITUDINAL PATH IN CONTACT WITH A FACE OF MINERAL MATERIAL TO BE EXTRACTED WHICH COMPRISES OPPOSITELY DISPOSED SPACED APART BASE MEMBERS INTERCONNECTED BY AND NORMALLY BIASED TOWARD EACH OTHER BY RESILIENT CONNECTING MEANS, OPPOSITELY DISPOSED GUIDE MEANS EACH PIVOTALLY CONNECTED AT ONE END TO A CORRESPONDING BASE MEMBER AND PIVOTALLY CONNECTED TO ONE ANOTHER AT THEIR OTHER ENDS BY A HINGE MEANS, THE LINEAR DISTANCE BETWEEN THE PIVOTAL CONNECTIONS OF SAID GUIDE MEANS TO SAID BASE MEMBERS BEING ADJUSTABLE LONGITUDINALLY, AND CUTTING MEANS DISPOSED ON SAID HINGE MEANS FOR CUTTINGLY ENGAGING AN ADJACENT FACE OF MINERAL MATERIAL TO BE EXTRACTED. 